1. Field of the Invention
This invention relates to compounds for modulating protein kinase enzymatic activity for modulating cellular activities such as proliferation, differentiation, programmed cell death, migration and chemoinvasion. Even more specifically, the invention relates to compounds which inhibit, regulate and/or modulate kinase signal transduction pathways related to the changes in cellular activities as mentioned above, compositions which contain these compounds, and methods of using them to treat kinase-dependent diseases and conditions.
2. Summary of Related Art
Improvements in the specificity of agents used to treat cancer is of considerable interest because of the therapeutic benefits which would be realized if the side effects associated with the administration of these agents could be reduced. Traditionally, dramatic improvements in the treatment of cancer are associated with identification of therapeutic agents acting through novel mechanisms.
Protein kinases are enzymes that catalyze the phosphorylation of proteins, in particular, hydroxy groups on tyrosine, serine and threonine residues of proteins. The consequences of this seemingly simple activity are staggering; cell differentiation and proliferation; i.e., virtually all aspects of cell life in one way or another depend on protein kinase activity. Furthermore, abnormal protein kinase activity has been related to a host of disorders, ranging from relatively non-life threatening diseases such as psoriasis to extremely virulent diseases such as glioblastoma (brain cancer).
Protein kinases can be categorized as receptor type or non-receptor type. Receptor-type tyrosine kinases have an extracellular, a transmembrane, and an intracellular portion, while non-receptor type tyrosine kinases are wholly intracellular.
Receptor-type tyrosine kinases are comprised of a large number of transmembrane receptors with diverse biological activity. In fact, about 20 different subfamilies of receptor-type tyrosine kinases have been identified. One tyrosine kinase subfamily, designated the HER subfamily, is comprised of EGFR (HER1), HER2, HER3, and HER4. Ligands of this subfamily of receptors identified so far include epithelial growth factor, TGF-alpha, amphiregulin, HB-EGF, betacellulin and heregulin. Another subfamily of these receptor-type tyrosine kinases is the insulin subfamily, which includes INS-R, IGF-IR, and IR-R. The PDGF subfamily includes the PDGF-alpha and beta-receptors, CSFIR, c-kit and FLK-II. Then there is the FLK family, which is comprised of the kinase insert domain receptor (KDR), fetal liver kinase-1 (FLK-1), fetal liver kinase-4 (FLK-4) and the fms-like tyrosine kinase-1 (flt-1). The PDGF and FLK families are usually considered together due to the similarities of the two groups. For a detailed discussion of the receptor-type tyrosine kinases, see Plowman et al., DN&P 7(6):334-339, 1994, which is hereby incorporated by reference.
The non-receptor type of tyrosine kinases is also comprised of numerous subfamilies, including Src, Frk, Btk, Csk, Abl, Zap70, Fes/Fps, Fak, Jak, Ack, and LIMK. Each of these subfamilies is further sub-divided into varying receptors. For example, the Src subfamily is one of the largest and includes Src, Yes, Fyn, Lyn, Lck, Blk, Hck, Fgr, and Yrk. The Src subfamily of enzymes has been linked to oncogenesis. For a more detailed discussion of the non-receptor type of tyrosine kinases, see Bolen, Oncogene, 8:2025-2031 (1993), which is hereby incorporated by reference.
Since protein kinases and their ligands play critical roles in various cellular activities, deregulation of protein kinase enzymatic activity can lead to altered cellular properties, such as uncontrolled cell growth, associated with cancer. In addition to cancer altered kinase signaling is implicated in numerous other pathological diseases. These include, but not limited to: immunological disorders such as rheumatoid arthritis, graft-host diseases, multiple sclerosis, psoriasis; cardiovascular diseases such as
atherosclerosis, myocardioinfarction, ischemia, stroke and restenosis; other inflammatory and degenerative diseases such as interbowel diseases,
osteoarthritis, macular degeneration, diabetic retinopathy. Therefore, both receptor and non-receptor protein kinases are attractive targets for small molecule drug discovery.
One particularly attractive goal for therapeutic use of kinase modulation relates to oncological indications. For example, modulation of protein kinase activity for the treatment of cancer has been demonstrated successfully with the FDA approval of Gleevec® (imatinib mesylate, produced by Novartis Pharmaceutical Corporation of East Hanover, N.J.) for the treatment of Chronic Myeloid Leukemia (CML) and gastrointestinal stroma cancers. Gleevec is a selective Abl kinase inhibitor.
Attractive targets for modulation include VEGF receptor 2 (Flk-1/KDR), FGFR1, and PDGFR (alpha and beta). These three receptor tyrosine kinases have been implicated in blood vessel formation and proliferation (angiogenesis). Angiogenesis is associated with and required for the growth of malignant solid tumors, and has also been implicated in the development of diabetic retinopathy and rheumatoid arthritis, for example, (see: Cherrington J M, Strawn L M, and Shawver L K. New paradigms for the treatment of cancer: the role of anti-angiogenesis agents. Adv Cancer Res (2000)79:1-38; Ciulla T A, et al. Ocular perfusion abnormalities in diabetes. Acta Ophthalmol Scand (2002) 80:468-77; Walsh D A, Haywood L. Angiogenesis: a therapeutic target in arthritis. Curr Opin Investig Drugs (2001) 2:1054-63, all incorporated by reference herein for all purposes). Therefore, compounds and their formulations that modulate such receptors should be useful in the treatment of cancer, rheumatoid arthritis and visual impairment due to diabetic retinopathy, as well as the other indications as outlined in paragraph [0007] above.
Evidence for a direct role of VEGF and its receptor (Flk-1/KDR) in angiogenesis has been well-documented. It has been shown that disruption of VEGF signaling (with either anti-VEGF antibodies or soluble VEGF receptors) can inhibit neovascularization and compromise existing tumor vasculature, resulting in inhibition of tumor growth (see: Hanahan D. Signaling vascular morphogenesis and maintenance. Science (1997) 277:48-50; Holash J, et al. Vessel cooption, regression, and growth in tumors mediated by angiopoietins and VEGF. Science (1999) 284:1994-8; Gale N W, Yancopoulos G D. Growth factors acting via endothelial cell-specific receptor tyrosine kinases: VEGFs, angiopoietins, and ephrins in vascular development. Genes Dev (1999) 13:1055-66, all incorporated by reference herein for all purposes). Also, several inhibitors of the kinase activity of Flk-1/KDR have shown anti-tumor activity in rodents (see: Laird, A. D. Cancer Res (2000) 60:4152-60; Wood, J. M., Cancer Res (2000) 60:2178-89, both incorporated herein for all purposes).
Kinases, FGF and PDGF, also play important roles in angiogenesis, sometimes in concert with VEGF. Although FGF knockout mice have no apparent defects related to impaired angiogenesis, FGF2 is clearly an angiogenic factor in vivo (see: Klint P, Claesson-Welsh L., Signal transduction by fibroblast growth factor receptors. Front Biosci (1999) 4:D165-77, herein incorporated by reference for all purposes). Also, FGF can act synergistically with VEGF to induce the expression of VEGF. Kinases, PDGF and PDGFR, are expressed in microvascular endothelial cells during angiogenesis (see: Sato N, et al. Platelet-derived growth factor indirectly stimulates angiogenesis in vitro. Am J Pathol (1993) 142:1119-30; Lindahl P, et al. Pericyte loss and microaneurysm formation in PDGF-B-deficient mice. Science (1997) 277:242-5, both incorporated by reference herein for all purposes). Like FGF, PDGF stimulates angiogenesis by up-regulating VEGF production. PDGF also stimulates the proliferation of pericytes and fibroblast-like cells surrounding endothelium. FGF and PDGF are also tumor cell mitogens, and their receptors are expressed in a variety of human cancers (see: Singh R K, et al. Cell density-dependent regulation of basic fibroblast growth factor expression in human renal cell carcinoma cells. Cell Growth Differ (1996) 7:397-404; Hermanson M, et al. Platelet-derived growth factor and its receptors in human glioma tissue: expression of messenger RNA and protein suggests the presence of autocrine and paracrine loops. Cancer Res (1992) 52:3213-9, both incorporated by reference herein for all purposes).
Accordingly, the identification of small-molecule compounds that specifically inhibit, regulate and/or modulate the signal transduction of kinases, for example VEGF receptor 2 (Flk-1/KDR), FGFR1, and PDGFR (alpha and beta), is desirable as a means to treat or prevent disease states associated with abnormal cell proliferation and is an object of this invention.